Add command line option to stop the assembler from padding the end of sections to...

	PR gas/20247
	* as.h (do_not_pad_sections_to_alignment): New global variable.
	* as.c (show_usage): Add --no-pad-sections.
	(parse_args): Likewise.
	* write.c (size_seg): Skip padding the end of the section if
	requested from the command line.
	(SUB_SEGMENT_ALIGN): Likewise.
	* doc/as.texinfo: Document the new option.
	* NEWS: Mention the new feature.
	* testsuite/gas/elf/section11.s: New test.
	* testsuite/gas/elf/section11.d: New test driver.
	* testsuite/gas/elf/elf.exp: Run the new test.

diff --git a/gas/NEWS b/gas/NEWS
index a0990602826158b9fd1633220081a16f55e40ebf..08807f18f1615c5ebf1413bac6a997bb9bdc3b95 100644 (file)
--- a/gas/NEWS
+++ b/gas/NEWS
@@ -1,4 +1,7 @@
 -*- text -*-
 -*- text -*-

+* Add --no-pad-sections to stop the assembler from padding the end of output
+  sections up to their alignment boundary.
+

 * Support for the ARMv8-M architecture has been added to the ARM port.  Support
   for the ARMv8-M Security and DSP Extensions has also been added to the ARM
   port.
 * Support for the ARMv8-M architecture has been added to the ARM port.  Support
   for the ARMv8-M Security and DSP Extensions has also been added to the ARM
   port.

diff --git a/gas/as.c b/gas/as.c
index badeac9bee329d9ab9f0e5580f98039b722fcd5e..8784fb481c06fa3a77793d739d087552845bea70 100644 (file)
--- a/gas/as.c
+++ b/gas/as.c
@@ -342,6 +342,8 @@ Options:\n\
   fprintf (stream, _("\
   -nocpp                  ignored\n"));
   fprintf (stream, _("\
   fprintf (stream, _("\
   -nocpp                  ignored\n"));
   fprintf (stream, _("\

+  -no-pad-sections        do not pad the end of sections to alignment boundaries\n"));
+  fprintf (stream, _("\

   -o OBJFILE              name the object-file output OBJFILE (default a.out)\n"));
   fprintf (stream, _("\
   -R                      fold data section into text section\n"));
   -o OBJFILE              name the object-file output OBJFILE (default a.out)\n"));
   fprintf (stream, _("\
   -R                      fold data section into text section\n"));


@@ -479,7 +481,8 @@ parse_args (int * pargc, char *** pargv)
       OPTION_REDUCE_MEMORY_OVERHEADS,
       OPTION_WARN_FATAL,
       OPTION_COMPRESS_DEBUG,
       OPTION_REDUCE_MEMORY_OVERHEADS,
       OPTION_WARN_FATAL,
       OPTION_COMPRESS_DEBUG,

-      OPTION_NOCOMPRESS_DEBUG
+      OPTION_NOCOMPRESS_DEBUG,
+      OPTION_NO_PAD_SECTIONS /* = STD_BASE + 40 */

     /* When you add options here, check that they do
        not collide with OPTION_MD_BASE.  See as.h.  */
     };
     /* When you add options here, check that they do
        not collide with OPTION_MD_BASE.  See as.h.  */
     };


@@ -542,6 +545,7 @@ parse_args (int * pargc, char *** pargv)
     ,{"MD", required_argument, NULL, OPTION_DEPFILE}
     ,{"mri", no_argument, NULL, 'M'}
     ,{"nocpp", no_argument, NULL, OPTION_NOCPP}
     ,{"MD", required_argument, NULL, OPTION_DEPFILE}
     ,{"mri", no_argument, NULL, 'M'}
     ,{"nocpp", no_argument, NULL, OPTION_NOCPP}

+    ,{"no-pad-sections", no_argument, NULL, OPTION_NO_PAD_SECTIONS}

     ,{"no-warn", no_argument, NULL, 'W'}
     ,{"reduce-memory-overheads", no_argument, NULL, OPTION_REDUCE_MEMORY_OVERHEADS}
     ,{"statistics", no_argument, NULL, OPTION_STATISTICS}
     ,{"no-warn", no_argument, NULL, 'W'}
     ,{"reduce-memory-overheads", no_argument, NULL, OPTION_REDUCE_MEMORY_OVERHEADS}
     ,{"statistics", no_argument, NULL, OPTION_STATISTICS}


@@ -637,6 +641,10 @@ parse_args (int * pargc, char *** pargv)
        case OPTION_NOCPP:
          break;
 
        case OPTION_NOCPP:
          break;
 

+       case OPTION_NO_PAD_SECTIONS:
+         do_not_pad_sections_to_alignment = 1;
+         break;
+

        case OPTION_STATISTICS:
          flag_print_statistics = 1;
          break;
        case OPTION_STATISTICS:
          flag_print_statistics = 1;
          break;

diff --git a/gas/as.h b/gas/as.h
index 51e16f11bf8f5aa03b73aa1f2293a8cfb6f4f187..169c714adb2cb61bd2bcaec792397f9b31ab1d81 100644 (file)
--- a/gas/as.h
+++ b/gas/as.h
@@ -76,8 +76,8 @@
    150 isn't special; it's just an arbitrary non-ASCII char value.  */
 #define OPTION_STD_BASE 150
 /* The first getopt value for machine-dependent long options.
    150 isn't special; it's just an arbitrary non-ASCII char value.  */
 #define OPTION_STD_BASE 150
 /* The first getopt value for machine-dependent long options.

-   190 gives the standard options room to grow.  */
-#define OPTION_MD_BASE 190
+   290 gives the standard options room to grow.  */
+#define OPTION_MD_BASE  290

 
 #ifdef DEBUG
 #undef NDEBUG
 
 #ifdef DEBUG
 #undef NDEBUG


@@ -377,6 +377,8 @@ COMMON int need_pass_2;
    leave lots of padding.  */
 COMMON int linkrelax;
 
    leave lots of padding.  */
 COMMON int linkrelax;
 

+COMMON int do_not_pad_sections_to_alignment;
+

 /* TRUE if we should produce a listing.  */
 extern int listing;
 
 /* TRUE if we should produce a listing.  */
 extern int listing;
 

diff --git a/gas/doc/as.texinfo b/gas/doc/as.texinfo
index 6d2c325798d585115f3e80aade9416838888f36c..9ebfda007101df6b269c0b67591039c776fafd02 100644 (file)
--- a/gas/doc/as.texinfo
+++ b/gas/doc/as.texinfo
@@ -235,6 +235,7 @@ gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
  [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
  [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
  [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}]
  [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
  [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
  [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}]

+ [@b{--no-pad-sections}]

  [@b{-o} @var{objfile}] [@b{-R}]
  [@b{--hash-size}=@var{NUM}] [@b{--reduce-memory-overheads}]
  [@b{--statistics}]
  [@b{-o} @var{objfile}] [@b{-R}]
  [@b{--hash-size}=@var{NUM}] [@b{--reduce-memory-overheads}]
  [@b{--statistics}]


@@ -773,6 +774,11 @@ Set the maximum width of an input source line, as displayed in a listing, to
 Set the maximum number of lines printed in a listing for a single line of input
 to @var{number} + 1.
 
 Set the maximum number of lines printed in a listing for a single line of input
 to @var{number} + 1.
 

+@item --no-pad-sections
+Stop the assembler for padding the ends of output sections to the alignment
+of that section.  The default is to pad the sections, but this can waste space
+which might be needed on targets which have tight memory constraints.
+

 @item -o @var{objfile}
 Name the object-file output from @command{@value{AS}} @var{objfile}.
 
 @item -o @var{objfile}
 Name the object-file output from @command{@value{AS}} @var{objfile}.
 


@@ -2158,6 +2164,7 @@ assembler.)
 * listing::       --listing-XXX to configure listing output
 * M::            -M or --mri to assemble in MRI compatibility mode
 * MD::            --MD for dependency tracking
 * listing::       --listing-XXX to configure listing output
 * M::            -M or --mri to assemble in MRI compatibility mode
 * MD::            --MD for dependency tracking

+* no-pad-sections:: --no-pad-sections to stop section padding

 * o::             -o to name the object file
 * R::             -R to join data and text sections
 * statistics::    --statistics to see statistics about assembly
 * o::             -o to name the object file
 * R::             -R to join data and text sections
 * statistics::    --statistics to see statistics about assembly


@@ -2494,6 +2501,15 @@ The rule is written to the file named in its argument.
 
 This feature is used in the automatic updating of makefiles.
 
 
 This feature is used in the automatic updating of makefiles.
 

+@node no-pad-sections
+@section Output Section Padding
+@kindex --no-pad-sections
+@cindex output section padding
+Normally the assembler will pad the end of each output section up to its
+alignment boundary.  But this can waste space, which can be significant on
+memory constrained targets.  So the @option{--no-pad-sections} option will
+disable this behaviour.
+

 @node o
 @section Name the Object File: @option{-o}
 
 @node o
 @section Name the Object File: @option{-o}
 


@@ -2680,7 +2696,7 @@ do include file processing with the @code{.include} directive
 (@pxref{Include,,@code{.include}}).  You can use the @sc{gnu} C compiler driver
 to get other ``CPP'' style preprocessing by giving the input file a
 @samp{.S} suffix.  @xref{Overall Options, ,Options Controlling the Kind of
 (@pxref{Include,,@code{.include}}).  You can use the @sc{gnu} C compiler driver
 to get other ``CPP'' style preprocessing by giving the input file a
 @samp{.S} suffix.  @xref{Overall Options, ,Options Controlling the Kind of

-Output, gcc.info, Using GNU CC} .
+Output, gcc info, Using GNU CC}.

 
 Excess whitespace, comments, and character constants
 cannot be used in the portions of the input text that are not
 
 Excess whitespace, comments, and character constants
 cannot be used in the portions of the input text that are not

diff --git a/gas/testsuite/gas/elf/elf.exp b/gas/testsuite/gas/elf/elf.exp
index 95c9204e4696de655945e1c04404812edb448ef2..3e85ae21646699c3e02c465331e2ba6cffe0ee23 100644 (file)
--- a/gas/testsuite/gas/elf/elf.exp
+++ b/gas/testsuite/gas/elf/elf.exp
@@ -205,6 +205,7 @@ if { [is_elf_format] } then {
     run_dump_test "section8"
     run_dump_test "section9"
     run_dump_test "section10"
     run_dump_test "section8"
     run_dump_test "section9"
     run_dump_test "section10"

+    run_dump_test "section11"

     run_dump_test "dwarf2-1"
     run_dump_test "dwarf2-2"
     run_dump_test "dwarf2-3"
     run_dump_test "dwarf2-1"
     run_dump_test "dwarf2-2"
     run_dump_test "dwarf2-3"

diff --git a/gas/testsuite/gas/elf/section11.d b/gas/testsuite/gas/elf/section11.d
new file mode 100644 (file)
index 0000000..c1043db
--- /dev/null
+++ b/gas/testsuite/gas/elf/section11.d
@@ -0,0 +1,13 @@
+#as: --no-pad-sections
+#readelf: -S --wide
+#name: Disabling section padding
+# The RX port uses non standard section names.
+#skip: rx-*-*
+
+#...
+  \[ .\] .text[        ]+PROGBITS[     ]+0+00 0+[0-9a-f]+ 0+0(1|4|5) 00  AX  0   0 16
+#...
+  \[ .\] .data[        ]+PROGBITS[     ]+0+00 0+[0-9a-f]+ 0+01 00  WA  0   0 16
+#...
+  \[ .\] .bss[         ]+NOBITS[       ]+0+00 0+[0-9a-f]+ 0+01 00  WA  0   0 16
+#pass

diff --git a/gas/testsuite/gas/elf/section11.s b/gas/testsuite/gas/elf/section11.s
new file mode 100644 (file)
index 0000000..200d34c
--- /dev/null
+++ b/gas/testsuite/gas/elf/section11.s
@@ -0,0 +1,14 @@
+.section .bss
+.balign 16
+.skip 1
+
+
+.data
+.balign 16
+.skip 1
+
+
+.text
+.balign 16
+.skip 1
+

diff --git a/gas/write.c b/gas/write.c
index 0dfca0c01c3b88d4b1201fd1be3b9bf0b4985a92..9af1f80f08fc4268bd86e9b22ed94537b8f383d4 100644 (file)
--- a/gas/write.c
+++ b/gas/write.c
@@ -579,7 +579,12 @@ size_seg (bfd *abfd, asection *sec, void *xxx ATTRIBUTE_UNUSED)
   x = bfd_set_section_flags (abfd, sec, flags);
   gas_assert (x);
 
   x = bfd_set_section_flags (abfd, sec, flags);
   gas_assert (x);
 

-  newsize = md_section_align (sec, size);
+  /* If permitted, allow the backend to pad out the section
+     to some alignment boundary.  */
+  if (do_not_pad_sections_to_alignment)
+    newsize = size;
+  else
+    newsize = md_section_align (sec, size);

   x = bfd_set_section_size (abfd, sec, newsize);
   gas_assert (x);
 
   x = bfd_set_section_size (abfd, sec, newsize);
   gas_assert (x);
 


@@ -1696,7 +1701,7 @@ set_symtab (void)
 }
 
 /* Finish the subsegments.  After every sub-segment, we fake an
 }
 
 /* Finish the subsegments.  After every sub-segment, we fake an

-   ".align ...".  This conforms to BSD4.2 brane-damage.  We then fake
+   ".align ...".  This conforms to BSD4.2 brain-damage.  We then fake

    ".fill 0" because that is the kind of frag that requires least
    thought.  ".align" frags like to have a following frag since that
    makes calculating their intended length trivial.  */
    ".fill 0" because that is the kind of frag that requires least
    thought.  ".align" frags like to have a following frag since that
    makes calculating their intended length trivial.  */


@@ -1708,6 +1713,7 @@ set_symtab (void)
    code-bearing sections.  */
 #define SUB_SEGMENT_ALIGN(SEG, FRCHAIN)                                        \
   (!(FRCHAIN)->frch_next && subseg_text_p (SEG)                                \
    code-bearing sections.  */
 #define SUB_SEGMENT_ALIGN(SEG, FRCHAIN)                                        \
   (!(FRCHAIN)->frch_next && subseg_text_p (SEG)                                \

+   && !do_not_pad_sections_to_alignment                                        \

    ? get_recorded_alignment (SEG)                                      \
    : 0)
 #else
    ? get_recorded_alignment (SEG)                                      \
    : 0)
 #else